The Vitamine Manual | Page 4

ordinary language this law states that
when a person eats a given amount of a given kind of food, that food
may liberate in the body practically the same amount of energy that it
would produce if it were burned in oxygen outside of the body. The
confirmation of this law permitted us to apply to the measurement of
food the same method we had already learned to use in measuring coal.
For convenience the physicists devised a heat measure unit for this
purpose and naturally called it by a word that means heat, namely,
"calorie." Using this unit and applying the isodynamic law it was
merely necessary to determine two things; first, how many calories a
man produces in any given kind of work, second how many calories a
given weight of each kind of food will yield, and then give the man as
many calories of food as he needs to meet his requirements when
engaged in a given kind of labor. The measurement and tabulation of
food values in terms of calories and the investigation of the calorie
needs of men and women in various occupations has been one of the
great contributions of the past twenty years of nutritional study and to
the progress made we owe our power to produce proper rations for
every type of worker. Army rations for example are built up of foods
that will yield enough calories to supply the needs of a soldier and
during the recent war extended studies conducted in training camps all
over the United States have shown that when the soldier eats all he
wants he will consume on the average about 3600 calories per day. In
France the American soldier's ration was big enough to yield him 4200
calories per day if he ate his entire daily allowance.
But calories are not the only necessities. A pound of pure fat will yield

all the calories a soldier needs in a day but his language and morals
wouldn't stand the strain of such a diet. Neither would his health, for
not only does his body demand fuel but also that it be of a special kind.
While there are many kinds of foodstuffs, chemical analysis shows that
they are mainly combinations of pure compounds of relatively few
varieties. The chemists call these proteins, fats, carbohydrates, and salts.
Meats, eggs, the curd of milk, etc., are the principal sources of protein.
Sugars and starches are grouped together under the name of
carbohydrate. By salts is meant mineral matters such as common salt,
iron and phosphorus compounds, etc. In selecting foods it was found
that the body required that the proportions of these four substances be
kept within definite limits or there was trouble. We know now that a
man can get along nicely if he eats 50 grams of protein per day and
makes up the rest of his calories in carbohydrates and fats, provided
that to this is added certain requirements in salts and water.
It is also obvious that the foods given must be digestible and palatable.
We had reached this status some time before 1911. But, a short time
before this, there had arisen a controversy as to the relative value of
different types of proteins. The animal- vs. vegetable-protein
controversy was one of the side shows of this affair. This controversy
had led to a careful study of the different kinds of proteins that are
found in foodstuffs. Through a brilliant series of chemical
investigations for whose description we haven't time or space here,
chemists had shown that every protein was built up of a collection of
acids which were different in structure and properties, that there were
some seventeen of these in all and that any given protein might have
present all seventeen or be lacking in one or more and that the
proportions present varied for every type of protein. It was then
obvious that proteins could not be considered as identities. More than
that, it was the necessary task of the food expert to separate all proteins
into their acids or building stones and not only show what was present
and how much but determine the rôle each played in the body. To this
task many set their faces and hands.
From the results there has accrued much progress in the evaluation of

proteins but an unexpected development was the part played by these
investigations in the story of the vitamines.
About 1909-1910 Professors Osborne and Mendel under a grant from
the Carnegie Institution began a detailed investigation into the value of
purified proteins from various sources. In their experiments they used
the white rat as the experimental animal and proceeded to feed these
animals a mixture consisting of a single purified protein supplemented
with the proper proportions of fat carbohydrate, and